Production of variable denier yarns of synthetic polymers

ABSTRACT

A PROCESS FOR MAKING VARIABLE DENIER YARN OF SYNTHETIC POLYMERS AT HIGH YARN PROCESSING SPEEDS COMPRISES DRAWING THE YARN WHILE VARIABLY HEATING THE SAME WITH A HOT GASEOUS MEDIUM SUCH AS A NARROW FLAME OR JETTED STREAM OF HOT GAS. EITHER THE YARN OR THE FLAME MAY BE DEFLECTED TO PRODUCE THE VARIABLE HEATING EFFECT.

Patented May 9, 1972 US. Cl. 264-167 12 Claims ABSTRACT OF THE DISCLDSURE A process for making variable denier yarn of synthetic polymers at high yarn plOcessirrg speeds comprises drawing the yarn while variably heating the same with a hot gaseous medium such as a narrow flame or jetted stream of hot gas. Either the yarn or the flame may be deflected to produce the variable heating effect.

The invention concerns improvements in or relating to the production of variable denier yarns of synthetic polymers.

Variable denier yarns of synthetic polymers are useful in providing the means of producing variable texture and dyeing effects in the fabrics made therefrom. Thus, mottled or other novelty effects can be produced when the fabric is dyed with a given dyestufi, owing to the varying rates and extents to which said dyestutf is taken up by the portions of different denier when such are the result of variable drawing.

Several ways in which variable denier yarns of synthetic polymers can be produced by variable drawing are described in United States patent specification No. 2,- 278,888, including, in Example V thereof, the way of intermittently contacting yarn of polyhexamethylene adipamide with a heated rod on passage of the yarn between feed and draw rolls.

Localisation of the point of drawing in the process of drawing yarns of synthetic polymers is usually achieved by wrapping the yarn around a stationary snubbing-pin positioned between the feed and the draw rolls. However, it is known from British patent specification No. 758,- 398 to substitute a jetted stream of hot gas for such a snubbing-pin.

Finally a process for producing variable denier yarns, which process includes the concept of drawing at below the natural draw ratio (viz the ratio across the neck at the point of drawing) has been described in United States patent specification Nos. 3,323,165 and 3,343,207. In these specifications, radiant heat energy is applied, randomly or periodically, to chosen segments of the yarn to raise their temperature above that required for uniform drawing thereof.

The use of mechanical devices for varying the amount of heat applied to the yarn, however, presents a serious disadvantage, due to inertia of mechanical parts, when it is required to programme precisely said heat application in order to obtain a yarn with a programmed pattern of portions with varying properties. Such a programme is arranged to give the most pleasing etfect in the final product and a pseudo-random pattern is particularly desirable in this respect. Clearly the higher the speed at which such operations are carried out the more serious this difliculty due to the inertia of the mass of parts of said mechanical devices becomes.

Applicants have now found that said difliculty with precise programming can be substantially overcome if the yarn itself, which has low inertia, is vibrated in a programmed manner in and out of contact with or proximity with a high temperature heat source or, preferably if a high temperature heat source of very low inertia, such as a portion of a jetted stream of hot gas or flame is moved in a programmed manner in and out of contact with or proximity with the yarn. It is to be understood that a gas stream or flame has regions of widely dilferent temperature and the yarn may be moved relatively to a very hot region without necessarily leaving the flame or gas stream altogether.

The present invention represents an improvement therefore on the prior art processes referred to above, in that it provides means whereby the required variability in denier of the yarn can be achieved at high rates of operation, owing to the low inertia of the system acted upon, and with such strength of effect that such variability can be achieved in a controlled programmed manner.

Accordingly the invention provides a process for the production of variable denier yarns of synthetic polymers comprising drawing undrawn yarn of a synthetic polymer between feed and draw rolls set to rotate at different speeds defining a mechanical draw ratio preferably lower than the natural draw ratio of said yarn and causing the yarn in the span between said feed and draw rolls and a heat source consisting of a portion of a narrow flame or a jetted stream of hot gas intermittently to approximate to or come in contact with each other according to a programme and in such a manner as to induce the formation of necks in said yarn.

Preferably, no snubbing-pin is employed in the process.

Applicants have found that while the desired effects are produced over a wide range of draw-ratios it is preferable to draw below the natural draw-ratio if a pronounced effect is desired.

In one embodiment of the invention the intermittent contacting or approximating of the yarn to a portion of the flame or hot gas stream may be brought about very simply by passing the yarn through a guide or guides on a vibrator, and thereby vibrating the yarn which has low inertia. The vibrator is preferably of the electromechanical variety which can be programmed electrically to vibrate according to any desired periodical or random or pseudo-random programme, which programme will be reproduced along the yarn in the length and spacing of the nubs (i.e. thick portions of substantially undrawn yarn). Instead of using a vibrator, the yarn path may be deflected by electro-static means.

Alternatively, the flame itself may be deflected according to a programme which gives the desired pattern of thick and thin portions in the yarn. This may be done e.g. electrostatically or by ionising the flame and varying a charge near it, or by imposing on it a sound pattern, for instance, in order to modulate it. In another method, the flame or hot gas stream, may be deflected by an impinging stream of gas which is modulated in a programmed manner.

When such yarns are woven into a fabric, and the fabric then dyed with a rate-sensitive dyestuff, a variegated fabric is obtained.

The flame is produced most readily by a gas burner. If a hot gas stream is preferred, saturated steam at substantially atmospheric pressure or hot air at a temperature of preferably at least 250 C. in a narrow jet is suitable for polyhexamethylene adipamide yarn. Clearly for a given yarn speed the temperature of the flame or gas stream should be high enough to obtain adequately quick respouse in the yarn, but not high enough to cause serious deterioration in yarn properties.

It is desirable for the flame or gas stream to impinge on the yarn at a distance from the draw roll slightly greater than the length of the longest nub desired.

The present invention may, if desired, be used in combination with other processes, such as varying plasticiser application, bulking or crimping of the yarn and the like, in order to obtain more complex desirable elfects. Furthermore, the drawing process may be part of a spin-draw process, wherein drawing follows immediately after spinning, without intermediate package formation.

From the aesthetic view-point desirable drawn yarn nub parameters, where the nubs are distributed in a pseudo-random pattern, are as follows:

Average nub length: 1-25 inches Average nub spacing: 1-100 inches Ratio of longest to shortest nub length: 1:1 to 12:1

{Ratio of longest to shortest nub spacing: 1:1 to :1

Average nub peak denier: 1.2 to 4 times the denier of the thin sections.

Particularly desirable parameters for a warp knitting yarn are:

Average nub length: -20 inches Average nub spacing: 10-40 inches Ratio of longest to shortest nut length: 2:1 to 4:1

Ratio of longest to shortest nub spacing: 2:1 to 4:1

Average nub peak denier: 1.5 to 4 times the denier of the thin sections.

Particularly desirable parameters for a yarn to be used as weft in weaving are:

Average nub length: 3-7 inches Average nub spacing: -45 inches Ratio of longest to shortest nut length: 2:1 to 4:1

Ratio of longest to shortest nub spacing: 2:1 to 4:1

Average nub peak denier: 1:5 to 4 times the denier of the thin sections.

The following examples illustrate the invention without in any way limiting it.

EXAMPLE I Undrawn multifilament yarn of polyhexamethylene adipamide containing 0.03% titanium dioxide and having 20 tri-lobal cross-section filaments and an undrawn denier of 270 was drawn at 1,200 feet/minute and at a mechanical draw ratio of 2.0. The yarn was periodically vibrated in and out of contact with a small gas/air flame, positioned between the feed and draw rolls at 18" from the draw roll, by means of an electromagnetic vibrator acting on guides through which the yarn was threaded. The periodic pulses applied to the vibrator were such that the yarn was removed from the flame for 8.5 milli-seconds and was held in the flame for 6.5 milli-seconds, giving nubs of 148 denier of 2.0 in length and spaced 3.8" apart, the denier between nubs being 56.

This periodic nub spacing in the yarn led to the appearance of extreme diamond barre in the fabric when the yarn was woven in the weft and after dyeing in a blue rate sensitive dyestufl, the general appearance being of dark blue streaks on a light blue ground.

EXAMPLE 2 The procedure of Example 1 was repeated, except that a draw ratio of 2.16 was used and the vibrator was supplied with pseudo-random pulses (i.e. such pulses as occur in a programme which is only repeated over a length of yarn such that the repeat is not visible in the fabric). Nubs between 4.8" and 11.8" (average 5.3) in length were obtained at spacing between 22.8" and 40" (average 24). When this yarn was woven as weft and dyed in a rate-sensitive blue duestutf, an aesthetically pleasing fabric was obtained with dark blue areas on a light blue ground. There was no evidence of periodicity.

EXAMPLE 3 575 denier/26 filament undrawn yarn of polyhexamethylene adipamide, containing 0.03% titanium dioxide, was drawn at 2,000 feet/minute at a draw ratio of 2.15 according to the arrangement of Example 2. Nubs were obtained between 3" and 9" (average 4") in length at spacings between 32 and 63" (average 35"). The average peak denier of the nubs was 545 and the denier of the lengths between nubs, 202, giving a ratio of 2.7.

When this yarn was woven as weft across a 205 denier/ 34 filament warp the resulting fabric showed slub-like variations in surface texture similar to the effect of including flax in the weft.

After dyeing in a rate-sensitive blue dyestufi, a fabric similar to that in Example 2 was obtained.

EXAMPLE 4 Nominally 205 denier 34 filament polyhexamethylene adipamide yarn, containing 0.3% titanium dioxide, was made by drawing 446 denier spun yarn to a ratio of 2.18 at 2,100 ft. per minute. A gas flame (approx. 0.05 diameter and 0.25 long) burning in a British Oxygen Company type 0 torch (Catalogue Reference 36587) with a 0.027 diameter jet, as supplied, replaced the snubber pin. This flame was located 18" before the draw roll. The yarn was withdrawn from the flame in a programmed manner according to periodic electrical pulses, the yarnwithdrawing pulses being 30 ms. long and spaced by ms. Various gas combinations were used as follows:

Yarn tempera- Ratio of average ture, C. nub peak denier (measured to that of the Gases pyrometrieally) thin sections (1) Coalgas and alr 65 1. 5 (2) Coal-gas and oxygen. 65 2. 1 (3) Propane and oxygen.- 70 2.30

Yarn temperatures were measured approximately 3" downstream of the flame with an infra-red Pyrometer.

The thick sections were 12.3 ins. long and spaced by 45 ins.

When weft-knitted and dyed in a rate-sensitive blue dyestufl the yarn made in conditions (1) showed less contrast between thick and thin section than (2) which was slightly less than (3). However, there was a pro nounced visible pattern in the fabrics made from all these yarns.

EXAMPLE 5 Average nub length (in.): 11, range (in.): 10-30 Average nub spacing (in.): 13, range (in.): 12-33 Ratio of average nub peak denier to that of the thin sections: 1. 8:1

Yarn mean extensibility: 98%

Tenacity: 3.4 g.p.d.

Denier (mean): 49

When weft-knitted and dyed with a rate-sensitive blue dyestuff this yarn gave an attractive variegated effect. No trace of periodicity was noted.

EXAMPLE 6 The apparatus of Example 4 was used to make a thickthin polyhexamethylene adipamide yarn of 205 mean denier. The spun yarn was 460 denier, with 34 filaments and contained 0.3% TiO This yarn was drawn to a ratio of 2.2 at 1,500 ft. per minute. The pseudo-random applied signal (pulse length 12 ms. range 11-35 ms.) (pulse spacing 72 ms., range 66-200 ms.) was displayed on one channel of a dual beam oscilloscope. The denier variation measured on the threadline, by a capacitance probe, after the drawing step, was displayed on the other channel. The display was photographed. The photographs were then cut so that the traces could be displaced relative to each other to account for the time taken for the yarn to pass from the flame to the measuring head. It was clearly seen that the denier variations corresponded exactly with the pseudo-random programme.

EXAMPLE 7 Using the apparatus of Example 4, except that the jet size was 0.011 in., a polyethylene terephthalate yarn containing 0.3% titanium dioxide was made under the following conditions:

Draw ratio: 2.40, draw speed: 2,500 ft./min. Pseudo-random programme Average pulse length: 12 ms. (range: 11-55 ms.) Average pulse spacing: 60 ms. (range: 55-160 ms.) Spun yarn denier: 208 Distance of flame to draw-roll: 30"

The correspondence of the denier variations with the imposed programme was confirmed using the method of Example 6.

The resultant yarn properties were:

Mean denier: 86.1

Tenacity: 2.39 g.p.d.

Extensibility: 66.7%

Average nub length: 6", range: 5.5-17.0 in.

Average nub spacing: 36", range: 34-95 in.

Ratio of average nub peak denier to that of the thin sections: 2.3:1

A weft knitted fabric from this yarn when dyed with a Waxalene Red dyestuff in acetone gave an attractive white and pale pink blotched effect. No periodicity was noted.

EXAMPLE 8 A propane-oxygen flame as in Example 4 replaced the snubbing-pin of a conventional drawtwister. A fine jet of compressed air was used perpendicular to this flame to blow the burning gases away from the yarn. The compressed air supply was switched pseudo-randomly on and off by a fluid logic element (Plessy Company, type RT) controlled by an electromagnetic relay.

The other conditions were:

Length of pseudo-random pulses: 80 ms., range: 73-225 Sparing of pseudo-random pulses: 420 ms., range: 380- Draw ratio: 2.0, drawing speed: 1,500 ft./min.

Spun yarn mean denier: 446 with 34 filaments Distance from flame to draw-roll: 60"

The resulting yarn had the following characteristics: Average nub length: 24" (range: 20-60 ins.) Average nub spacing: 146" (range: 137-200 ins.) Ratio of average nub peak denier to that of the thin sections: 1.8:1 Tenacity 2.1 g.p.d.: extensibility 92% A weft-knitted fabric produced from this yarn and dyed in a rate-sensitive blue dyestuff showed attractive light and dark blue areas with no sign of periodicity.

EXAMPLE 9 Polyhexamethylene adipamide yarn containing 2% TiO of spun denier 93 and 15 filaments, was drawn using the apparatus of Example 4 with a propane-oxygen flame. The conditions were as follows:

(1) Drawing speed: 2,600 ft./rnin. at a draw ratio of 2.19. (2) Applied electrical pulses:

(a) Length: 23 ms. (constant) (b) Spacing: 23 ms. (17-56 ms. range) (Pseudorandomly distributed) Distance of flame from draw-roll: 18 inches The resulting yarn had the following characteristics: Average nub length: 11.0 (range: 10.5-11.5") Average nub spacing: 11.0" (range: 9"-28") Ratio of average nub peak denier to that of the thin sections: 2.0 :1 Tenacity: 3.9 g.p.d. at 75% extension This yarn was used to construct a warp for knitting. The resulting fabric showed a novel varying opacity. 0n subsequent dyeing in a rate-sensitive green dyestulf a pleasing two shaded fabric resulted.

What I claim is:

1. In the process of drawing undrawn yarns of synthetic polymers by applying a hot gaseous medium to the yarn to induce a necking down effect as the yarn passes between feed and draw' roll means, the improvement which comprises imparting variable denier in the yarn by causing the yarn and the hot gaseous medium intermittently to approximate to or come in contact with each other according to a program to thereby vary the formaion of necks in the yarn and form nubs along the length of the yarn.

2. A process as claimed in claim 1 wherein the programme is a pseudo-random programme.

3. A process as claimed in claim 1 wherein the yarn is spun and drawn in one continuous process.

4. A process as claimed in claim 1 wherein the yarn is drawn below its natural draw ratio.

5. A process as claimed in claim 1 wherein the programme is controlled by a pseudo-random signal generator.

6. A process as on claim 1 wherein the hot gaseous medium has regions of diiferent temperature and is selected from the group consisting of a narrow flame and a jetted stream of hot gas.

7. A process as in claim 6 wherein the yarn is deflected relative to the gaseous medium by passing the yarn in contact with a yarn guide and electromagnetically vibrating the yarn guide.

8. A process as in claim 6 wherein the yarn is electrostatically deflected relative to the gaseous medium.

9. A process as in claim 6 wherein the hot gaseous medium impinges on the yarn at a distance from the draw roll means slightly greater than the length of the longest nub desired.

10. A process as in claim 6 wherein the hot gaseous medium is electrostatically deflected relative to the yarn.

11. A process as in claim 6 wherein the hot gaseous medium is deflected relative to the yarn by impinging a varying stream of gas on the flame.

12. A process as in claim 6 wherein the hot gaseous medium is sonically deflected relative to the yarn.

References Cited UNITED STATES PATENTS 1,526,387 2/1925 Mettler 28-63 2,108,361 2/1938 Asakawa 26423 (Other references on following page) UNITED 7 STATES PATENTS Peterson et a1. 264-23 Deboutteville 264-23 Rodenacker 264-23 Sabato et a1. 264-24 Burklund 28-12 Stoller 28-12 Knee 264-24 Marrinan et a1. 264-290 T Yano et a1. 264-167 Mottern et a1. 264-167 8 Mottern et a1. 264-167 Nakagawa et a1. 264-167 Pital 264-290 Marlborough et a1. 264-290 Bird et a1. 264-210 JAY H. WOO, Primary Examiner US. Cl. X.R.

10 18-1 FT; 28 72.-12, 72:17; 57 140 J; 161-179; 

